Synthetic-grass coverings have been used for quite some time now, in particular to provide areas of greenery for urban decoration and similar amenities, for areas for bordering swimming-pools, and, in general, for replacing natural-grass cover in all those conditions where the laying and maintenance of a natural-grass cover may prove critical. The use of said synthetic-grass coverings has received new impulse in recent times in order to provide coverings for sports facilities, for example soccer pitches. The corresponding literature is extremely extensive, as is witnessed, at a patent level, by documents such as: U.S. Pat. Nos. 3,731,923, 4,337,283, 5,958,527, 5,961,389, 5,976,645, JP-B-32 53 204, JP-A-10037122, DE-A-44 44 030, EP-A-0 377 925 and U.S. Pat. No. 6,887,535 (to which there corresponds EP-A-1 158 099).
In particular, from the document mentioned last, which is filed in the name of the present applicant, a synthetic-grass structure is known, which comprises a sheet-like substrate with a plurality of filiform formations extending from the substrate for simulating the grassy sward of natural turf and a particulate filling material, or infill, dispersed between the filiform formations so as to keep the filiform formations themselves in a substantially upright condition. Specifically, the above synthetic-grass covering is characterized in that the particulate filling material (infill) is constituted by a substantially homogeneous mass of a granular material chosen in the group constituted by polyolefin-based materials and by vinyl polymer-based materials.
Further advantageous developments of the above solution are described in the documents Nos. EP-A-1 319 753, EP-A-1 375 750, EP-A-1 371 779, as well as EP-A-1 486 613, all of said documents being owned by the present applicant.